When your hairs start turning gray, the water bottle should be your mainstay — at least while exercising. New research shows that middle-aged and older adults should drink more water to gain the full benefits of exercise.

Image credits Gustavo Jeronimo / Wikimedia.

Few things will ruin your workout quite like dehydration. Even if you power through and keep to your routine despite the cottonmouth, you won’t benefit that much from it: dehydration has been shown to impair exercise performance and brain function in young people. However, the effect of dehydration during exercise for older individuals was poorly studied, and thus poorly understood, as there are some key metabolic differences between these age groups.

“Middle-age and older adults often display a blunted thirst perception, which places them at risk for dehydration and subsequently may reduce the cognitive health-related benefits of exercise,” the authors wrote.

Age slows down our metabolic rate, meaning we need fewer calories. Coupled with the fact that we generally tend not be as physically active as we age, elderly people tend to experience a decrease in appetite too. By eating less food, they get less hydration from solid food sources — humans generally get about half their daily water requirement from solid foods, as well fruit and vegetable juices.

To get a better understanding of how this impacts the health benefits of exercise, the New England-based team of researchers recruited recreational cyclists who took part in a large cycling event on a warm day (78-86°F or 25.5-30°C). The participants’ average age was 55.

The cyclists were asked to go through a “trail-making” executive function test: they had to connect numbered dots on a piece of paper, being graded both on their speed and accuracy. Executive functions are a set of processes that all have to do with managing oneself and one’s resources in order to achieve a goal. They include the ability to plan, focus, remember, and multitask. Exercise has been shown to improve intellectual health, including executive function.

The team also tested the volunteers’ urine before they exercised, and divided them into two groups based on the results — either in the ‘normal hydration’ or the ‘dehydrated’ groups.

Those in the normal hydration group showed a noticeable improvement in completion speed of the trail-making test after cycling (relative to their initial results). The dehydrated group also completed the task more quickly after cycling, but the difference in completion times wasn’t significant, the researchers noted.

“This suggests that older adults should adopt adequate drinking behaviors to reduce cognitive fatigue and potentially enhance the cognitive benefits of regular exercise participation,” the researchers wrote.

The paper “Dehydration impairs executive function task in middle-age and older adults following endurance exercise” was presented on Sunday, April 22, at the American Physiological Society (APS) annual meeting Experimental Biology 2018 in San Diego.